Steps to reproduce the issue

Step1. Create an article sub-category under Uncategorised, named sub.
Step2. Create a category's custom field group, named test.
Step3. Create a text type category's custom field (or watever type), assign to category "Uncategorised".
Step4. Fill in category sub's custom field. Then unpublish the category and close.
Step5. Click into category sub's edit page. The test tab is disappeared.
Step6. Publish category sub, the tab comback but all data erased.

Expected result

Un-publishing a category with custom field should work like un-publishing an article.

Actual result

Unpublish category makes its custom field tab disappear and data erased

System information (as much as possible)

Joomla! 3.9.23, or eariler
php7.3x
MariaDB10.5.8-

Additional comments

It will be alright if assign the custom field to ALL categories, or child category (sub).
This also happens in J4.0.0 beta4